The present invention concerns a high-pressure pump, and a high-pressure injection system.
In high-pressure injection systems for internal combustion engines, in particular in common rail injection systems of diesel or petrol engines, a high-pressure pump permanently maintains the pressure in the high-pressure accumulator of the common rail injection system. The high-pressure pump may be driven for example by a camshaft of the internal combustion engine by means of a drive shaft. To deliver the fuel to the high-pressure pump, pre-delivery pumps are used, e.g. a gear or rotary vane pump, which are connected upstream of the high-pressure pump. The pre-delivery pump delivers the fuel from a fuel tank through a fuel line to the high-pressure pump.
Amongst others, piston pumps are used as high-pressure pumps. A drive shaft is mounted in a housing. Pistons are arranged in a cylinder radially to said drive shaft. A running roller with a roller rolling face mounted in a roller shoe lies on the drive shaft having at least one cam. The roller shoe is connected to the piston so that the piston is forced into an oscillating translational movement. A spring applies to the roller shoe a force directed radially toward the drive shaft, so that the running roller is in constant contact with the drive shaft. The running roller with the roller rolling face makes contact with the drive shaft on a shaft rolling face as a surface of the drive shaft having the at least one cam. The running roller is mounted in the roller shoe by means of a plain bearing. The longitudinal and movement axes of the oscillating pistons arranged in a V-shape have no axial spacing in the direction of the rotation axis of the drive shaft, so that the running rollers of several pistons roll overlapping on the shaft rolling face of the drive shaft. The life of the high-pressure pump is primarily limited by the number of rolls performed by the rollers on the shaft rolling face of the drive shaft, because the number of rolls determines the mechanical wear on the shaft rolling face. Since several, for example two, rollers roll overlapping on the shaft rolling face, with two running rollers, a full revolution of the drive shaft by 360° about the rotation axis of the drive shaft equates to two rolls of the running rollers on the same shaft rolling face. Disadvantageously, the high-pressure pump thus has a short life.
DE 10 2006 045 933 A1 discloses a high-pressure pump for high-pressure fuel delivery. The high-pressure pump has a drive shaft with cams. Cylindrical rollers supported by roller shoes lie on the cams. The roller shoes are mounted in a bore in part of the housing by means of a tappet assembly. The pump elements are attached to the tappet assembly. A coil spring presses the tappet assembly onto the cams.
DE 103 56 262 A1 discloses a radial piston pump for creating a fuel high-pressure in fuel injection systems in internal combustion engines. A drive shaft is mounted in a pump housing. Pistons rest on the drive shaft so that rotation of the drive shaft moves the pistons to and fro. Tappets are arranged between the pistons and the drive shaft.
EP 2 299 114 B1 describes a pump device for an internal combustion engine. The pump device comprises a pump housing, at least one delivery arrangement which has a delivery piston for pressurizing fuel in a pump chamber, a drive shaft carrying a cam and a cam lobe which cooperates with the delivery arrangement to drive the pistons along a piston axis, and a plate which is coupled by coupling means on one side to the cam lobe and on the other side to the housing.
DE 10 2007 002 730 B4 discloses a radial piston pump for fuel delivery in a fuel injection system of an internal combustion engine, comprising a drive shaft mounted rotatably in a pump housing and having an eccentrically formed shaft portion on which a tappet is mounted slidably and cooperates with at least one piston foot of a piston, which is arranged in a respective cylinder chamber radially relative to the drive shaft for the reciprocating motion in the direction of the piston axis. The tappet has a tappet cross section running only partially around the eccentric shaft portion.